Many technologies have been employed in order to visualize or locate cardiac tissue in the beating heart, including ultrasound, contrast enhanced fluoroscopy, electrical sensors, and direct visualization via a small camera or endoscope surrounded by a transparent fluid such as saline.
Each of these technologies is has its limitations, including resolution, contrast-induced nephropathy (CIN), and/or fluid overload, among others. Resolution with transesophageal echo (TEE) can be insufficient, while at the same time it is difficult to obtain an absolute orientation, given the degrees of freedom of the probe. Electrical sensors can be effective to signal contact with tissue, but are prone to error when used to determine depth of penetration below the surface of the tissue. In addition to CIN mentioned above, fluoroscopic interpretation is made more difficult by the transient nature of the contrast injection, and can be exacerbated further by the shape of the heart chamber. For example, fluoroscopic short axis views of the left ventricle can be difficult to interpret for patients with conditions such as heart failure or mitral valve regurgitation. These conditions can necessitate the use of a larger volume of contrast to obtain an adequate image. The inability to precisely assess the cardiac tissue in a beating heart renders it difficult to perform procedures with the precision needed to adequately treat these patients.